Circulating pump for steam generators



- 27 1942. M. SPILLMANN 2,271,352,

CIRCULATING PUMP FOR STEAM GENERATORS Filed Jan. 4, 1940 3 Sheets-Sheet l J I1/////////////////) 1 r r//// A Max Spillmafln ENTOR ATTORNEY Jan. 27, 194 2. SPILLMANN 2,271,352.

\ I CIRCULATING PUMP FOR STEAM GENERATORS Filed Jan. 4, 1940 3 Sheets-Sheet 2 ex 5 IN NTO I I. I i i Patented Jan. 27, 1942 UNITED STATE CIRCULATING PUMP FQR STEAM GENERATORS Max Spillmann,

Worthington Pump an tion, Harrison, N. J., a corporation of Delaware Application January 4, 1940, Serial No. 312,369 Claims. (c1. insits) This invention relates to centrifugal pumps,

and more particularlyto a pump for circulating the water through a steam generator or boiler in a forced circulation system steam generator.

- In forced circulation boilerfeed systems, such as the 'La Mont, etc., the water is circulated through the economizer or first section of the tubes of a boiler or steam generator and is picked up from this set of tubes and/or a steam drum by a circulating pump and forced under increased pressure through the evaporator section or remaining tubes of the boiler.

The tubes in the boiler of such a system are arranged, together with the circulation arrangement of the water, in such a manner that each tube receives the correct amount of water, according to its steam generating capacity, as determined by its position in the system.

Such forced circulation systemsteam genera-' tors have many advantages over the natural circulation type steam generators, especially in in;

stallations where maximum steam generation per unit of space andweight is required, which fact has been recognized in the field; However, considerable difficulty has been experienced in providing an efficient, practical pump for handling the circulated water at the temperatures and pressures necessary to provide the proper operation of such a forced circulation of water through the boiler Particular difficulty has been experienced in providing'a practical and eflicient Clifton, N. l, assignor to d Machinery Corporanately on opposite sides of the circulating pump impeller, with the highest stage impellers adjacent to the circulating impeller and between the circulating impeller and the stufiing boxes of the pump. This arrangement protects the stuffing boxes from action of leakage of the high temperature, high pressure fluid from the circulating pump impeller.

- With these and other objects in view, as may appear from the accompanying specification, the

invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a circulating pump for steam generators, of the preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

- In the drawings: I

Figure l is adiagrammatic view showing a steam generating plant having the improved pump associated therewith.

Figure 2 is a longit dinalsection through the improved pump.

Figure 3 is a fragmentary longitudinal section through the pump. taken at Various angles packing for sucha pump against the tempera? tures and pressure of the water pumped.

The primary object of the present invention is to provide a pump which will meet all of the requirements of such a boiler feed system, and which is particularly designed to overcome the packing and leakage difliculties prevalent in pumps heretofore employed in such systems.

More specifically, the present invention comprises a combined boiler feed pump and forced circulation circulating pump in a single casing, with stage impellers of the boiler feed pump capable of developing pressures somewhat in ex- 7 cessto the discharge of the circulating pump,

or at least greater than thesuction pressure of the circulating pump, and arranged to create a back pressure or leakage pressure towards the circu- I l'ating impeller to prevent leakage of the high temperature, high pressurefiuid from the circulating pump. The stage impellers of the boiler feed pump are arranged with the'lowest stageimpellers disposed adjacent to the ends of the pump casing and the intermediate stage impellers arranged so that successive stages lie alterthrough the pump to'permitillustration of the suction and discharge passages of the pump.'

Referring more particularly to the drawings, a steam generatorof the La Mont forced circulation type is diagrammatically illustrated in Fig. 1 of the "drawings and in the operation of such a steam generator the boiler feed water passes first through the'economizer section 1 of the tube arrangement of the boiler. From the economizer section I of the boiler the water passes into the steam drum 2, where it is picked up by the forced circulation circulating pump and discharged through the evaporator section 3 ofthe tube arrangement of the boiler. If it is so desired, the steam from the steam drum may be passed through .a superheater 4 and from thence through the steam outlet pipe 5 to the point at which the steam is to be used. The type of steam generator just disclosed is a particular type-of forced circulation generator; but it isto be understood that the improved pump comprises the The improved pump is shown in plan in Figure 1 of the drawings and in section in the other views, and it comprises a pump casing l0, through w ich the driving shaft ll extends axially. The

driving shaft I! has a prime mover such as an electric motor or the like, |2, connected to its driving end. The pump combines both the boiler feed pump and the forced circulation pump in the single casing I0, having a plurality of boiler feeding impellers 20, 2|, 22 and 23 mounted on the shaft rotatable thereby, and disposed in the casing I in equal sets on opposite sides of the circulating impeller or pump 25. The boiler feeding impellers 20, 2|, 22 and 23 are arranged with the lowest stage impellers, namely impellers and 2|, disposed adjacent to the ends of the casing i0, and. the intermediate impellers arranged so that the stages lie alternately on opposite sides of the circulating pump impeller 25. That is, the suction 26 of the boiler feed pump enters the first stage impeller 20 at one end of the casing Ill. The first stage impeller 20 discharges itsliquid through its discharge volute and a carry-over passage 2'1, into the inlet 28 of the second stage impeller 2 I The second stage impeller 2| discharges through its discharge volute 29 and a suitable carry-over passage 30- sure to the boiler feedwater may be employed in a pump of the present invention, without departing from the spirit thereof.

By particular reference to Figure 2 of the drawings, it will be noted that the impellers 20 and 22 on one side of the circulating impeller'25 face in one direction, while the impellers 2| and 23 of the other side onv the circulating pump 25 face in the opposite direction. This arrangement of the boiler feeding impellers servesa dual function. It provides for counter-balancing of the end thrust in the pump, and also it positions the two intermediate or highest pressure stage impellers with their backs towards the impeller 36 of the circulating pump 25, so that leakage from the boiler feed pump impellers will befrom the discharge of these two highest pressure stages towards the impeller 36, thus setting up a counv 38 will thusbe subjected to the lowest pressures in the pump, and'consequently the packing of the pump will be greatly facilitated.

The boiler feed pumpimpellers and the final stage impeller thereof, 23, discharge through the discharge outlet 39 and discharge line 40 to the economizer section of the steam generator. The suction opening 4| of the circulating pump 25 has connection through a suitable piping 42 to the steam drum 2 and the impeller 36 of the circulating pump 25 picks up the water from said steam drum 2 and discharges it through the discharge 43 of the circulating pump 25 through a suitable connection to the evaporator section 3 of the steam generator.

As shown in Figures 2 and 3 of the drawings, the impeller 36 of the circulating pump 25 is a a double suction impeller, having its suction eyes facing towards the two inner-most stages of the boiler feed pump, and as a consequence the suction passage to the pump 25 is divided, as shown at 45 and 46, to deliver water from the steam drum 2 to both suction inlets of the impeller 36. The impeller 36 discharges into a single discharge volute 41, which in turn discharges into the discharge passage 43.

The foregoing is predicated on a boiler feed pump which develops a pressure per square inch of discharge of its two last stages equal to or in excess of the suction pressure of the circulating pump; however practical and advantageous results have been obtained in pump structures according to the present invention wherein the discharge pressure of the final stage of the boiler feed pump is in excess of the discharge pressure of the circulating impeller, while the discharge pressure of the next to the last stage impeller which is on the opposite side of the circulating impeller is slightly less than the discharge presure of the circulating impeller.

For example, in a steam generator system wherein the boiler drum pressure is 1000 p. s. 1., the discharge pressure of the final stage'of the boiler feed pump would be 1150p. s. i. and the discharge of the circulating pump would be 1050 p. s. i. while the discharge of the next to the last stage of the boiler feed pump may be 950 p. s. 1. Thus the counter-acting back pressure on the one side of the circulating impeller would be p. s. i. in excess of its discharge pressure, while on the other side it would be approximately'lOO p. s. 1. less, and slightly less than the suction pressure of the circulating pump. This may permit some leakage into the next to the last stage a of the boiler feed pump which would, however, be

absorbed therein before reaching the packing at the suction end of the pump.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1; In a pump for forced circulation system steam generators, a pump casing, a plurality of boiler feed water pumping stage impellers in said casing, a circulating'impeller in said casing for forcibly circulating feed water through a portion of a steam generator, a commondriving shaft for all of said impellers, stufling boxes about said shaft, certain of said boiler feed water feeding impellers disposed between the circulating impeller and said stufling boxes and capable of developing a pressure approximately equal to the pressure developed by the circulating impeller, said boiler feeding impellers arranged whereby leakage from them will counter-act leakage from the circulating impeller.

2. In a pump for forced circulation system steam generators, a casing, a plurality of successive stageimpellers and discharge volutes therefor in said casing, said -impellers arranged with the lowest stage impellers disposed adjacent to the ends of the casing and the intermediate stage impellers progressively'arranged from the lowest stages to the final discharge stage impeller intermediate thereof, a circulating impeller in said casing for forced circulation of water through a part of a steam generator, the intermediate stage impellers of said plurality of stage impellers arranged alternately on opposite sides of said circulating impeller, said intermediate stage impellers of said plurality ofstage impellers being in said casing, a circulating impeller in said sealing gland structure.

constructed and arranged tFcreate a counterbalancing pressure against leakage of the circulating impeller. v 3. In a pump for forced circulation system steam generators, a casing a plurality of successive stage impellers and discharge volutes therefor in said casing, said impellers arranged witharranged alternately on opposite sides of said circulating impeller, stuffing boxes carried by said casing, said plurality of stage impellers constructed and arranged to create a counter-acting pressure leakage against leakage of the circulating impeller to prevent leakage of the circulating impeller contacting the stuffing boxes.

4. In a pump for forced circulation system steam generators, a casing, a plurality of successive stage impellers and discharge volutes therefor in said casing, said impellers arranged with the lowest stage impellers disposed adjacent to the ends of the casing and the intermediate stageimpellers progressively arranged from the lowest stages to the final discharge stage 1 impeller intermediate thereof, a circulating 'impeller in said casing for forced circulation of water through a part of a steam generator, the intermediate stage impellers of said plurality of stage impellers arranged alternately on opposite sides of said circulating impeller, said circulating impeller being a double suction impeller, and

the stage impellers adjacent'to the circulating impellerv having their discharge sides facing the inlets of the circulating impeller, said stage impellers being capable of. developing a pressure approximately equal to the suction pressure of the circulating impeller. 1

5. In a pump for forced circulation system steam generators, a casing, a shaft therein. a plurality of boiler feed water said casing for forceably circulating feed water through a portion of the steam generator, said circulating impeller being adapted to receive Water at high inlet temperatures and pressures, a sealing gland structure between said shaft and casing,'said boiler feed water pumping impellers arranged between the suction inlet of said cir-v culating impeller and said sealing gland structure and being of such size as to be capable of developing a pressure approximately equal to the suction pressure of the circulating impeller to build up a counterbalancing' pressure against leakage from the circulating impeller towards 6. In a pump for forced circulation system steam generators, a casing, a shaft in said casing, sealing structures between said shaft and casing, a circulating pump in said casing for receiving liquid at high inlet pressure, and pump I impellers on said shaft on each side of said circulating pump and being of such size ranged relative to the circulating pump to provide a counteracting pressure against leakage pumping impellers and arfrom the circulating pump towards-said sealing structures.

'7. In a pump for forced circulation system steam generators, a casing, a shaft in said casing,-

a circulating impeller on said shaft and adapted to receive liquid at high inlet pressures, pump impellers on said shaft on each side of said circulating impeller and capable of developing pressures approximately equal to the pressures of said circulating impeller and arranged on said shaft relative to said circulating impeller to provide a counteracting pressure against leakage from the circulating impeller along said shaft.

8. In a pump. a casing, an impeller in said casing for receiving liquids at high inlet pressures, and other impellers in said casing for receiving liquids at inlet pressures lower than the inlet pressures of said first-named impeller, said low inlet pressure impellers being of sufficient size to develop counteracting pressures approxi mately equal to the leakage pressures and said low inlet pressure impellers being arranged to direct said counterbalancing pressure against leakage of said first-named impeller.

9. In a pump, a casing, a double suction impeller in said casing for receiving liquids at high inlet pressures, single suction impellers, in said casing on each side of said double suction impeller and capable of developing pressures approximately equal to the suction pressure of. the double suction impeller and arranged with respect to the circulating impeller to'set up counteracting pressures against leakage from the double suction impeller.

10. In a pump, a casing, a driving shaft in said casing, a double suction impeller in said casing for receiving liquids at high inlet pressures, single suction impellersin said casing on each side of said double suction impeller, sealing structures between said casing and shaft, outwardly of said single suction impellers, said single suction -impellers being of such size and pumping characteristics as to develop pressures approximately equal to the suction pressures of the double suction impeller and to set up counterbalancing pressures against leakage from the double suction impeller towards said sealing structures.

11. In a pump,-a casing, a shaft in said casing, a plurality of successive stage impellers and discharge volutes therefor in said casing, said successive stage impellers arranged with the lowest stage impellers disposed adjacent to the ends of the casing and the intermediate stage impellers progressively arranged from the lowest stages to the final discharge stage impeller intermediate thereof, a double suction impeller in said casing for receiving liquids at high inlet pressures, the intermediate stage impellers of said plurality of stage impellers arranged alternately on opposite sides of said double suction impeller, the stage impellers adjacent to the double suction impeller having their discharge sides facingithe inlets of the double suction impeller, said stage impellers receiving liquids at pressures below the suction pressure of said double suction impeller and being capable of developing a pressure approximately equal to the suction pressure ofthe double suction impeller for setting up counterbalancing pressure against leakage from the double suction impeller. I r

"12. In a pump for forced circulating system steam generators, a plurality of feed water. pumping impellers for initially deliverying feed water to a steam generator, a circulating'impeller for receiving water delivered to a steam generator by said feed water pumping impellers for forcibly circulating the water through a portion of the steam generator, whereby the" circulating impeller receives water at its suction at a temperature in excess of the temperature discharged by said feed water pumping impellers and at a pressure slightly less than the highest discharge pressure of the feed water pumping impellers, said feed water pumping impellers disposed relative to the circulating impeller so that discharge pressure leakage from the feed water pumping impellers will be toward the suction'of the cir-. culating impeller tocreate a counterbalancing pressure against suction pressure leakage from the circulating impeller.

13. In a pump for forced circulating steam generators, a casing, a shaft extending through said casing, packing about said shaft at the ends of the casing, a plurality of feed water pumping impellers in said casing for initially delivering feed water to a steam generator and having their suction inlets facing the packing whereby the packing will be subjected to the lowest pressures in the pump, a circulating impeller on said shaft between said feed water pumping impellers and having its suction inlet facing the discharge preswater pumping impellers, said feed water pump-- ing impellers disposed relative to the circulating impeller so that discharge pressure leakage from the feed water pumping impellers will be toward the suction of the circulating impeller to create a counterbalancing pressure against suction pressure leakage from the circulating impeller.

14. In a pump, a casing, a shaft extending through said casing, a circulating impeller on said shaft and capable of receiving liquid at high pressure at its suction and raising the pressure of the liquid a proportionately small amount to cause forced circulation of the liquid passing through the impeller, pumping impellers on said shaft on each side of said circulating impeller and capable of imparting relatively high pressure increase to liquid handled thereby, the suction of said circulating impeller facing the highest pressure discharge of said pumping impellers whereby counterbalancing leakage pressures between the suction of the circulating impeller and the discharge of the pumping impellers will be set up. i

15. In a pump, a casing, a shaft extending through said casing, packing about said shaft at the ends of said casing, a circulating impeller on said shaft and capable of receiving liquid at high pressure at its suction and raising the pressure of the liquid a proportionately small amount to cause forced circulation of the liquid passing through the impeller, pumping impellers on said shaft on each side of said circulating impeller and capable of imparting relatively high pressure increase to liquid handled thereby, the

suction of said circulating impeller facing the subject to the lowest pressures in the casing.

MAX

SPIL'LMANN. 

